Lunar Trailblazer was a small (class D) lunar orbiter, part of NASA's SIMPLEx program, with a mission to detect and map water on the lunar surface to determine how its form, abundance, and location relate to geology.[5] Its mission is to aid in the understanding of lunar water and the Moon's water cycle. Lunar Trailblazer was launched on 27 February 2025, as a secondary payload on the IM-2 mission.[6] The Principal Investigator (PI) of the mission is Bethany Ehlmann, a professor at Caltech.[7] Soon after launch, NASA lost contact with the spacecraft.
Lunar Trailblazer was selected to be part of NASA's Small Innovative Missions for Planetary Exploration (SIMPLEx) program in 2019. The goal of the planned mission is to use a small satellite to map water on the Moon.[8]
measure and map the amount, location and form (hydroxyl, H2O, or ice) of lunar water and determine any correlation to latitude and surface makeup
study the time-variability of lunar water in sunlit portions of the Moon
determine the form, amount, and location of lunar water in permanently shadowed parts of the Moon
study how changes in surface temperature affect concentrations of water and ice[9]
In addition, the spacecraft was to search for good locations for future lunar landings.
Launch and mission outcome
Like other SIMPLEx missions, Lunar Trailblazer was launched as a "rideshare" with another NASA or commercial mission. It was launched as a secondary payload on the IM-2 mission in February 2025 with a number of other payloads.[6] Originally it was going to launch with IMAP in 2025, but NASA found a different rideshare opportunity since the spacecraft was scheduled to be completed in 2022.
Soon after launch, NASA lost contact with the spacecraft.[10]As of 4March2025[update] attempts were still being made to contact the spacecraft.[11]
Orbit
Lunar Trailblazer was to orbit the Moon in a 100 kilometres (62 mi) polar orbit to study water on the Moon using its two scientific instruments.[7]
Unshielded from the vacuum of space, lunar landscapes are exposed to full illumination from the Sun for about two weeks, and total darkness for another two weeks. The Moon's day—one full rotation—is equivalent to about twenty eight Earth days. Adding to the harshness of this surface environment, the Moon has almost no atmosphere and no magnetosphere to protect it from the Sun's radiation. So, the lunar surface undergoes extreme temperature swings every day and night. During the day, temperatures near the equator are well above boiling, up to 400 K, or 260°F.[12] At night, these latitudes reach temperatures far below freezing (around 170 K/-150°F at most). Any water that reaches the surface during the night would be expected to boil away during the day, or quickly sublime away in the low pressure.
On the Moon, there is no rainfall, but there are other ways that water can be delivered to the surface: micrometeorite impacts can carry water from space or excavate water from below the surface, and potentially, water could be created directly on surface minerals by implantation of hydrogen from the solar wind.[13] Still, until very recently, scientists did not expect water to be present on most of the surface of the Moon.
In 1998, Feldman et al.[14] showed that water ice might be present in permanently shadowed craters at the poles of the Moon. They detected the presence of hydrogen in the upper half-meter (1.5 feet) of the lunar surface, which was most likely evidence of water ice. This discovery was debated in the scientific community as missions to study the lunar surface waned and further data was unavailable—until, in 2009, LCROSS (Lunar Crater Observation and Sensing Satellite) jettisoned one of its empty propellant tanks in a controlled collision to impact an area of the Moon that lay in permanent shadow to test for the presence of ice. When the tank hit, it created a plume that was observed by both the LRO (Lunar Reconnaissance Orbiter) and the LCROSS spacecraft as well as telescopes on Earth. Tremendous amounts of data were captured from the observed plume, including signatures of water ice and other volatiles.[15]
Also in 2009, researchers reviewing data from three separate spacecraft—Chandrayaan-1,[16]Deep Impact,[17] and Cassini[18]—extracted a hydration signature throughout the whole lunar surface. This was a surprise to the lunar science community, particularly because this meant that water may be present on boiling-hot sunlit portions of the Moon. However, the instruments gathering the spectral data weren't designed to look for water, and did not have enough resolution in the 3-micron band of infrared light for researchers to distinguish between the absorption features of hydroxyl (OH), H2O, and water ice. Lunar Trailblazer's instruments are specifically designed to detect and distinguish between these three forms of water.[19]
Spacecraft
The Lunar Trailblazer spacecraft was built and tested by Lockheed Martin. It uses two deployable solar arrays, which provide 280watts of power, and a chemical propulsion system. With its solar panels fully extended it was 3.5 meters (11 ft) long. The spacecraft weighed 200 kilograms (440 lb). It carried two science instruments, High Resolution Volatiles and Minerals Moon Mapper (HVM3), and the Lunar Thermal Mapper (LTM). HVM3 was provided by JPL and the LTM was provided by the University of Oxford.[5]
Science payload
There are two scientific instruments on the Lunar Trailblazer satellite, totaling 20kg. The High Resolution Volatiles and Minerals Moon Mapper (HVM3) was to gather and map shortwave infrared spectral data of the lunar surface. Simultaneously, Lunar Thermal Mapper (LTM) was to acquire midwave infrared data.[5] Together, the two instruments were to create a simultaneous map of the surface mineral composition, temperature, and forms of lunar water,[20] each measuring at least one thousand targets on the lunar surface over the course of the satellite's one-year primary mission.[21]
High Resolution Volatiles and Minerals Moon Mapper (HVM3)
The HVM3 instrument was developed by the Maturation of Instruments for Solar System Exploration (MatISSE) program, and was manufactured by the Jet Propulsion Laboratory.[5] It is a pushbroomshort-wave infraredimaging spectrometer based on the design of the M3 instrument, which was one of the instruments to first find evidence of hydration in sunlit regions of the Moon.[21] HVM3 has a spectral range from 0.6 to 3.6 microns—it is designed to work with high sensitivity (10nm resolution) right at the center of water's key wavelength region in infrared light (from 2.5 to 3.5 microns) with high enough spectral resolution to differentiate between forms of water.[21][5] Each pixel in an image from HVM3 could cover 50–90 meters (160–300ft) of the lunar surface.[5]
Lunar Thermal Mapper (LTM)
The LTM instrument was designed and built by the University of Oxford.[5] With eleven narrow channels between 7 and 10 microns and resolution smaller than 0.5 microns, it acquires multispectral images to characterize the Si-O stretch in silicates to derive mineralogical composition.[5] At the same time, using the four broadband channels from 6 up to 100 microns, it could derive surface temperature with a precision of 5K (9°F/5°C) in the range of 110–400K (-262 to 260°F/-163 to 126°C).[5][22] The pixel size of LTM is 40–70 meters.[5]
↑ Feldman, W. C.; Maurice, S.; Binder, A. B.; Barraclough, B. L.; Elphic, R. C.; Lawrence, D. J. (4 September 1998). "Fluxes of Fast and Epithermal Neutrons from Lunar Prospector: Evidence for Water Ice at the Lunar Poles". Science. 281 (5382): 1496–1500. Bibcode:1998Sci...281.1496F. doi:10.1126/science.281.5382.1496. PMID9727973.
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